1. Field of the Invention
The invention pertains to the field of switch mechanisms that facilitate online replacement of printed circuit board cards, such as peripheral component interface (PCI) cards. The switch mechanisms also function as a mechanical latch.
2. Discussion of the Related Art
Computer system maintenance, repair and upgrade operations frequently involve the insertion or replacement of expansion cards. For example, an expansion card that provides a specific functionality may be inserted into a PCI or ISA bus. This card may be replaced for a variety of reasons including system upgrades or failure of the card.
Standard operating procedures for the insertion or replacement of expansion cards have traditionally required the computer system to be shut-down or powered off during the insertion or replacement procedures. This requirement is problematic because the computer system is unavailable to fulfill its intended function during the procedure. The system unavailability is not necessarily a problem is some cases, however, unavailability causes severe disruptions in other cases. For example, in the case of a telecommunications server that supports a large number of clients, even temporary unavailability of the server may cause extreme inconvenience to the client base.
One solution to the problem of having to shut down computer systems for maintenance is to provide an online or hot-swapping capability that permits the insertion and removal of expansion cards while the system is operational. For example, U.S. Pat. No. 5,568,610 teaches the use of capacitive plates coupled to corresponding variable frequency oscillators that, in combination, detect the insertion or removal of an expansion card. U.S. Pat. No. 6,252,514 describes a sliding lock assembly coupled with a detector that is capable of notifying the system when the lock assembly is engaged or disengaged, in order to prepare the system for selective insertion or removal of an expansion card. Similarly, U.S. Pat. No. 6,247,080 describes a method of hot-swapping peripheral adapters
A current industry trend is to provide two switches for the hot-swapping or online replacement of PCI cards. A first switch is known as a xe2x80x9cdoorbellxe2x80x9d switch that an operator manually depresses to notify the system that the card is to be removed. The system, as needed, then saves states and commences an orderly shutdown of either the individual card. A second switch is used to unlatch the card from its location inside the chassis and, if the card is still under power at the time of unlatching, sends a signal that require the system to shut off power to the card before electrical damage can occur to the card.
While mechanisms and methods for the hot-swapping of expansion cards or peripheral adapters are known in the art, various problems arise in connection with the use of known mechanisms. For example, mechanisms that require the provision of a hole in a computer chassis or housing also produce a corresponding electromagnetic interference leak emanating from the hole. Furthermore, the layout of the switches and latching mechanisms is often ergonomically inconvenient.
There remains a need to provide an ergonomically improved switch and latch mechanism for use in online replacement of PCI cards and other expansion cards, that does not require openings which result in an EMI leak, and occupies only a small footprint.
The present invention overcomes the problems that are outlined above by providing an improved switch/latch mechanism which presents itself for easy viewing during use during online replacement of PCI cards and other expansion cards, does not require openings which result in an EMI leak, and occupies a small footprint.
The switch/latch mechanism according to the various embodiments and instrumentalities described herein retains a generally planar printed circuit board having a forward end, a rearward end, and an L-shaped bulkhead mounting bracket. The L-shaped mounting bracket has a first bracket segment that is connected to the forward end of the printed circuit board, and a second bracket segment extending forward of the first segment.
In an embodiment that is further described below, the switch/latch mechanism comprises a bulkhead adapted for mating engagement with the bulkhead mounting bracket of the peripheral card when the peripheral card is installed in the switch/latch mechanism. The bulkhead includes a first bulkhead wall that is oriented in parallel to the first bracket segment, and a second bulkhead wall that is oriented in parallel to the second bracket segment when the peripheral card is installed in the switch/latch mechanism. The second bulkhead wall includes an alignment pin for use in positioning the second bracket segment on the second bulkhead wall. A switch housing is deployed on a forward end of the second bulkhead wall. The switch housing includes a first switch wall parallel to the first bulkhead wall, and a second switch wall parallel to the second bulkhead wall. A paddle switch is mounted on the switch housing through use of a hinge axis that permits the paddle switch to travel in an arcuate path of motion over the second bulkhead wall. The hinge axis oriented in parallel to the first switch wall, so that the arcuate path of motion extends between a locked position of normal operation engaging the alignment pin, and an interrupt position remote from the alignment pin. A doorbell switch is mounted in the second switch wall and has a range of motion perpendicular to the second switch wall between an extended position of normal use and a compressed position.
In particularly preferred embodiments, the paddle switch includes a flag arm and a first optical switch component internal to the switch housing. The first optical switch component has a first slot permitting passage of the flag arm for optical interrupt purposes when the paddle switch is in one of the locked position of normal operation engaging the alignment pin and the interrupt position remote from the alignment pin. The paddle switch may include a snap mechanism for engaging the alignment pin when the panel switch is placed in the locked position of normal operation.
The doorbell switch has an interrupt arm and a second optical switch component internal to the switch housing. The second optical switch component has a second slot permitting passage of the interrupt arm for optical interrupt purposes when the doorbell switch is in one of the extended position of normal use and the compressed position. The doorbell switch may also comprise an integrally formed spring biasing the doorbell switch into the extended position of normal use.
The first slot and the second slot may be placed in transverse orientation with respect to one another, to provide an extremely compact assembly that occupies a very small footprint. The compact assembly permits the system chassis to occupy a lower vertical profile or, for example, the same profile may now contain an air venting structure, such as a perforated wall rising above the switch housing.
The switch/latch mechanism preferably includes a plurality of paddle switch and doorbell switch pairs attached to the switch housing. Each pair is allocated to a corresponding peripheral bus.
The switch housing may be advantageously formed using a modular construction comprising successive units each capable of housing a portion of the plurality of paddle switch and doorbell switch pairs. The successive units may, for example, comprise clip latch structure for engaging the second bulkhead wall to retain the successive units in fixed location with respect to one another.